Finding self catering accommodation in New Zealand is extremely easy. New Zealand is full of specifically those types of accommodation that are either fully self catering or offer self catering options. Kiwis like holidaying, like travel in their own country and like the freedom of self catering accommodation options.
Self catering accommodation options include:
(1) Holiday Parks
These are usually a cross between a hotel, motel, caravan park and a campsite, offering a variety of accommodation ranging from tent and camper van sites to cabins, cottages and motels. Each of these will allow for self catering, with some having a kitchen as a part of self-contained unit and some having some cooking provision (usually a fridge, microwave, kettle and toaster) while the kitchen is available in the communal part of the park. Strangely, there are cabins that are not en suite (i.e. have no bathroom or toilets) but have kitchen provision. Even motels that don't offer holiday park type variety of options usually have some cooking facilities.
(2) Self catering cottages and cabins
Cottages and cabins often come as part of the Holiday Parks, but there are also many independent ones, offering standards varying from basic to luxurious.
Hostels always have a communal kitchen, and in New Zealand often a backpackers' hostel will also have a motel section run at the same site as well as self-catering cabins or cottages.
How to find those self catering options?
The first step is to look online. New Zealand's official tourist information site will give pointers, while there are countless websites that will show you what's available. Many of these accommodations have their pages on travel sites such as this one where you can also check reviews by people who actually stayed there.
On the ground, all cities and many towns in New Zealand have official tourist information sites (i-site) which are very happy to advise on accommodation and provide listings, contact numbers and more brochures that you will be able to carry.
Among the best sources of information are AA accommodation guides that can be picked up for free in most motels and other accommodation providers. These list options by location and type and are an excellent source of info. Your travel guide (Rough Guide and Lonely Planet are reliably good and always provide a good selection of budget and mid range options) will also have some suggestions. And finally, in small places you can usually simply drive through and find a place as you arrive – usually well sign posted from main roads.
Do you need to book?
You definitely need to book in the high holiday season, i.e. December and January. Book early: six months early might not be too early for popular destinations. It's also advisable to book, especially in busier and more touristy places, in November and February. Outside these periods, you should be able to find something at a short notice without trouble, but if you have your eyes set on anything in particular, it's always better to book in advance.